The onset of the Paleolithic Period has traditionally coincided with the first evidence of tool construction and use by Homo some 2.5 million years ago, near the beginning of the Pleistocene Epoch (about 2.6 million to 11,700 years ago). In 2015, however, researchers excavating a dry riverbed near Kenya’s Lake Turkana discovered primitive stone tools embedded in rocks dating to 3.3 million years ago—the ... (100 of 998 words)